This section provides background information related to the present disclosure which is not necessarily prior art.
Internal combustion engines may combust a mixture of air and fuel in cylinders and thereby produce drive torque. Air and fuel flow into and out of the cylinders may be controlled by a valvetrain. Valvetrains typically include a camshaft that actuates intake and exhaust valves and thereby controls the timing and amount of air and fuel entering the cylinders and exhaust gases leaving the cylinders. In overhead camshaft (OHC) valvetrains, the camshaft is located in a cylinder head above the combustion chambers and typically actuates the intake and exhaust valves via lifters coupled to the intake and exhaust valves.
Engines having multiple intake and/or exhaust valves in each cylinder may include a dual OHC valvetrain configuration. Dual OHC valvetrains typically include a first camshaft that actuates the intake valves and a second camshaft that actuates the exhaust valves. Typically, the camshafts include a lobe corresponding to each of the respective intake and exhaust valves that controls the valve timing. Some camshafts are concentric camshafts that provide for relative rotation between first lobe members and second lobe members that actuate the valves. The first lobe members may be fixed to a tubular outer shaft for rotation with the outer shaft. The second lobe members may be radially supported by the outer shaft and may be fixed for rotation with an inner shaft. The inner shaft may be disposed within the outer shaft and may be radially supported by the outer shaft.
A cam phaser may be coupled to the outer shaft and the inner shaft and may control a relative rotational position between the outer shaft and the inner shaft. In this manner, the cam phaser may be used to adjust the overall timing of the valves by varying the duration of valve opening. A timing wheel may be coupled to one of the outer shaft and the inner shaft and may be used to sense a rotational position of the corresponding shaft.